1. Field of the Invention
The invention concerns an electro-optic device including a waveguide.
2. Description of the Prior Art
An electro-optic device usually comprises metal electrodes for applying a field or injecting a current across an optical waveguide. One is in the immediate vicinity of the guide and can therefore affect the propagation of the optical modes which are guided therein. This causes deformation and/or attenuation of these modes and can therefore compromise the operation of the device.
Without prejudice to the general nature of this problem, it will be better understood with reference to the case of a polarization converter. The function of a converter of this kind is to cause a transfer of energy by an electro-optical effect between the TE and TM modes of a waveguide. An electric field created in a "pin" type junction using metal layer electrodes is used for this purpose. The presence of a layer of metal near the guide may seriously disturb the interaction predicted by theory between the TE and TM optical modes and the applied electric field because this layer deforms and/or attenuates the two optical modes, possibly in different ways.
An object of the invention is to provide a simple waveguide electro-optic device which at least partially avoids some unwanted interactions without its efficiency being compromised. The interactions concerned are those which may occur between a wave travelling through a waveguide formed in a plate and the conductive material of a locating electrode formed on the plate to localize within the waveguide a wanted electrical phenomenon such as a field or a current.